1. Field of the Invention
The invention relates to a terminal box device for a solar cell module and a connecting method for such a terminal box device.
2. Description of the Related Art
A known system for generating solar energy arranges solar cell modules in matrix on a roof of a house or the like. Terminal box devices are provided for connecting the solar cell modules with other solar cell modules.
Japanese Unexamined Patent Publication No. 2002-252356 discloses a known terminal box device with built-in bypass diodes. The bypass diodes are connected in parallel with solar cells contained in the solar cell module and are reverse-biased with respect to the output polarity of the respective solar cells. A current of this solar cell is bypassed to the bypass diode if a reverse bias voltage is applied to the solar cell.
Other technologies relating to the terminal box device for a solar cell device are disclosed in Japanese Unexamined Patent Publication No. 2002-57360, Japanese Unexamined Patent Publication No. 2001-119058 and Japanese Unexamined Patent Publication No. H11-26035.
The diode in the aforementioned terminal box device generates heat due to the current flowing therethrough. For example, the terminal box device disclosed in Japanese Unexamined Patent Publication No. 2002-252356, has a plurality of adjacent diodes connected in series and disposed in a single casing. This entire solar cell module takes a negative polarity. Thus, adjacent diodes may experience a synergistic thermal influence by each other to increase the temperature of the diodes considerably if the currents run through all the diodes connected in series. Diodes that reach an abnormally high temperature in this way may, in a worst-case scenario, be short-circuited.
Moreover, the aforementioned diode has a poor thermal conductivity since the upper lead plate is formed with slits and a waist portion and is relatively thin. Thus, heat developed by the rectifying-element main body is difficult to radiate from the upper lead plate to the outside, and a junction temperature of the rectifying-element main body is likely to increase.
In view of the above problem, an object of the present invention is to suppress or reduce temperature increases of rectifying elements.
The invention relates to a terminal box device for a solar cell module. The terminal box device comprises a terminal box casing. Connecting terminals are arranged in the terminal box casing and are connected with a plurality of connecting elements from photoelectric conversion elements of the solar cell module. Two of the connecting terminals are adapted to connect with a pair of connection cables so that the connection cables can be drawn out from the terminal box casing. The terminal box casing comprises accommodating spaces for accommodating rectifying elements to be connected electrically between the adjacent connecting terminals, and the respective rectifying elements are to be connected in series via intermediate terminal mounts in the terminal box casing. Thus, heat developed in the rectifying elements becomes difficult to transfer to the adjacent rectifying elements. Accordingly, temperature increases of the rectifying elements due to the mutual thermal influence of the rectifying elements are suppressed.
The terminal box device may further have at least one partition wall partitioning the accommodating spaces for the respective rectifying elements.
A filler preferably is filled at least partly in the terminal box casing and/or an air layer is formed inside the partition wall.
The terminal box device may further comprise a partition wall for partitioning the rectifying elements and a filler in the terminal box casing. The partition wall suppresses heat transfer through the filler, and temperature increases of the rectifying elements are suppressed more effectively.
The terminal box device may further comprise a partition wall in the terminal box casing for partitioning the respective rectifying elements, and an air layer may be formed inside the partition wall. Accordingly, heat transfer from one rectifying element to another is suppressed by the air layer in the partition wall, and temperature increases of the rectifying elements are suppressed more effectively.
The connecting terminals may be arranged substantially side by side at substantially even intervals and the intermediate terminal mounts may be arranged at the outer sides of the respective connecting terminals. Accordingly, a plurality of connecting elements from the photoelectric conversion elements of the solar cell module can be connected at substantially even intervals.
A pin-shaped connecting member may be used between the intermediate terminal mount and the connecting terminal connected with the intermediate terminal mount. Accordingly, heat transfer from the rectifying element to other rectifying elements via the pin-shaped connecting member is suppressed, and temperature increases of the rectifying elements are suppressed more effectively.
A non-linear connecting member may be used between the intermediate terminal mount and the connecting terminal that is connected with the intermediate terminal mount. Accordingly, heat becomes difficult to transfer from one rectifying element to another, and temperature increases of the rectifying elements are suppressed more effectively.
Part of the nonlinear connecting member may be located outside the terminal box casing. Accordingly, heat is radiated at a portion of the connecting member outside the terminal box casing and heat becomes difficult to transfer from one rectifying element to another. Thus, temperature increases of the rectifying elements are suppressed more effectively.
The invention also relates to a terminal box device for a solar cell module. The terminal box device comprises a terminal box casing with a plurality of rectifying element accommodating spaces for accommodating a plurality of rectifying elements. Each rectifying-element has a main body, a first lead terminal and a second lead terminal that has a better thermal conductivity than the first lead terminal. The terminal box device also includes a plurality of terminal pairs corresponding to the number of the rectifying elements. Each terminal pair includes a first terminal to be connected with the first lead terminal, a second terminal to be connected with the second lead terminal, and at least one radiating intermediate terminal for connecting at least one pair of the first and second terminals to be connected with the adjacent rectifying elements such that the respective rectifying elements can be connected in series. Accordingly, the terminal box device for a solar cell module has an excellent property of radiating the heat of rectifying elements.
The invention also relates to a terminal box device for a solar cell module where rectifying elements are provided in a terminal box casing. Each rectifying element has a main body with first and second electrodes. A first lead terminal is connected with the first electrode, and a second lead terminal is connected with the second electrode. The second lead terminal has a better thermal conductivity than the first lead terminal. Terminal pairs are provided and correspond to the number of the rectifying elements. Each terminal pair has a first terminal connected with the first lead terminal and a second terminal connected with the second lead terminal. At least one radiating intermediate terminal for connecting the first and second terminals is connected with the adjacent rectifying elements such that the respective rectifying elements are connected in series.
As described above, heat developed by the rectifying-element main body is transferred from the second lead terminal having a relatively higher heat radiating property to the second terminal and then further to the first terminal connected with the adjacent rectifying element via the radiating intermediate terminal. The heat is radiated in these respective heat transfer paths. Thus, the rectifying element has a good heat radiating property.
The first lead terminal may be a plate, and the second lead terminal may be made to have a better thermal conductivity than the first lead terminal by forming the first lead terminal with a smaller cross-sectional area than the second lead terminal. For example, the first lead terminal may be thinner than the second lead terminal and/or the first lead terminal may have at least one slit and/or the first lead terminal may have a waist portion. Accordingly, thermal stresses on portions connecting the rectifying-element main body and the first and second lead terminals can be alleviated since the first lead terminal is easily resiliently deformable.
The first terminal, the second terminal and/or the radiating intermediate terminal may be substantially flat plates. Accordingly, heat can be radiated efficiently from the first terminal, the second terminal and the radiating intermediate terminal.
The radiating intermediate terminal preferably is formed integrally or unitarily with the first terminal and/or the second terminal for intermediate connection. Accordingly, an assembling operability of the terminal box device is improved and heat can be transferred more efficiently to provide a better heat radiating property.
The invention also relates to a method for connecting a lead terminal and a terminal in a terminal box casing of a terminal box device. The terminal box device may be one of the above-described terminal box devices for a solar cell module. The terminal box device may include a terminal box casing for a plurality of rectifying elements each including the lead terminal and the terminal to be connected with the lead terminal. The method preferably comprises placing the terminal and the lead terminal one over the other with solder therebetween. The method then includes holding a pair of electrodes in contact with the lead terminal and the terminal and applying a current between the pair of electrodes to heat the solder, thereby soldering the lead terminal and the terminal. Accordingly, the solder between the lead terminal and the terminal is heated to solder the lead terminal and the terminal.
Alternatively, the method may employ resistance welding. Thus, the lead terminal and the terminal are joined merely by applying a current between the electrodes. Thus, the connecting operation is performed in a relatively short period.
This connecting method can be applied in a case where at least one of the first and second lead terminals is connected with the corresponding one of the first and second terminals upon producing the terminal box device for a solar cell module.
The method may include forming operation holes in portions of the terminal box casing where the lead terminal and the terminal are to be connected. The rectifying elements and the terminal may be fixedly accommodated in the terminal box casing, and the electrodes may be brought into contact with the lead terminal and the terminal through the operation holes, thereby connecting the lead terminal and the terminal by soldering and/or resistance welding.
These and other objects, features and advantages of the invention will become more apparent upon reading of the following detailed description of preferred embodiments and accompanying drawings. It should be understood that even though embodiments are separately described, single features thereof may be combined to additional embodiments.